The role of optical spectral measurements for the monitoring of static and dynamic fluid systems is well established in the field of spectroscopy. Traditional systems may include the use of a spectrometric measurement system, such as a spectrometer or photometer, optically interfaced to a fluid stream, such as a liquid or gas. In the case of spectrometer systems, commercial dispersive near-infrared (NIR) or Fourier transform infrared (FTIR, near- and mid-IR) instruments often utilize various optical sensors used in transmission, transflectance (a combination of transmittance and reflectance) and internal reflectance modes of operation. U.S. Pat. No. 7,339,657, hereby incorporated by reference in its entirety, discusses each of these modes of operation as implemented into various optical sensor packages.
More generally, optical spectroscopy, for example, in the form of infrared spectroscopy is a recognized technique for the analysis and characterization of various types of fluids used in industrial, automotive and transportation applications, including lubricants, functional fluids and diesel emission fluids (DEF), which is marked under the ADBLUE® trademark of Verband der Automobilindustrie E.V. (VDA). Such spectroscopic measurements can provide meaningful data about the condition of the fluid and the fluid system during service. The term infrared spectroscopy is used in the broadest sense, and includes both near infrared and mid-infrared, and covers the region from 700 nanometers (nm) to 25,000 nm.
Infrared spectroscopy, as defined above, can provide measurement of fluid quality, such as DEF quality, and fluid properties, by way of example only, oxidation, coolant contamination, fuel dilution, soot, and content. In most cases, this information is derived directly as a measure of the chemical functionality, as defined by the characteristic vibrational group frequencies observed in the near infrared and infrared spectra. Further, the UV and visible spectra may provide information derived from color and/or information derived from electronic transitions and can be applied to provide information about oxidation, moisture and additive content, by way of example.
While the infrared spectral region is definitive in terms of the measurement of materials as chemical entities, the measurements can be difficult to implement in terms of the materials used. More specifically, the optics and associated materials used in these measuring devices are relatively expensive and do not always lend themselves to easy replication for mass production.
Moreover, when multiple devices are implemented into a larger monitoring system used in, for example, automotive monitoring applications, these systems often become prohibitively large, complex, and expensive. Another factor to consider is the operating environment. If a monitoring system is to be used in a relatively benign environment, such as in a laboratory under standard ambient conditions or in a climate conditioned indoor facility, then a device construction of the prior art may be used. However, if there is a requirement to measure a fluid system in a less conducive environment, such as on a process line (indoors or outdoors), on a vehicle, or a mobile or fixed piece of equipment, then it is necessary to consider a system more capable of operating under such conditions. This may include considering the temperature sensitivity of the components, as well as their robustness in terms of long-term exposure to continuous vibrations. Additional factors for consideration include size, thermal stability, vibration immunity and cost.
Alternative fluid measurement systems and techniques for fluid sensing and monitoring that address one or more of these considerations are desired.